From the Centers for Disease Control. Influenza activity--United States, 1989-1990.
D000368:Aged; D004196:Disease Outbreaks; D006760:Hospitalization; D006801:Humans; D009980:Influenza A virus; D007251:Influenza, Human / Q000453:epidemiology*; D008875:Middle Aged; D014481:United States / Q000453:epidemiology